Wireless access systems have been widely deployed to provide various types of communication services such as voice or data. In general, a wireless access system is a multiple access system that supports communication of multiple users by sharing available system resources (a bandwidth, transmission power, etc.) among them. For example, multiple access systems include a Code Division Multiple Access (CDMA) system, a Frequency Division Multiple Access (FDMA) system, a Time Division Multiple Access (TDMA) system, an Orthogonal Frequency Division Multiple Access (OFDMA) system, and a Single Carrier Frequency Division Multiple Access (SC-FDMA) system.
Recently, a wireless access network configuration has been changed such that various types of small cells having small sizes such as a pico cell, a femto cell, etc. interact with a macro cell having a relatively large size. The wireless access network configuration aims to provide a high data rate to final UEs and thus increase Quality of Experience (QoE) for the final UEs in a situation where multi-layer cells co-exist in a hierarchical structure basically involving a macro cell.
According to one of the current 3rd Generation Partnership Project (3GPP) standardization categories, Small Cell Enhancements for E-UTRA and E-UTRAN SI; e.g., RP-122033, enhancement of indoor/outdoor scenarios using low-power nodes is discussed under the title of small cell enhancement. In addition, scenarios and requirements for the small cell enhancement are described in 3GPP TR 36.932.
In consideration of the aforementioned trend, final UEs will be more closely positioned at a network in a physical manner in the future in a manner of arranging many numbers of small cells to the inside of a macro cell. Hence, it is expected that communication via a UE-centered zone is enabled instead of a legacy physical cell-based communication in a next generation wireless access network. In order to perform the communication via the UE-centered zone for enhancing capacity, it is necessary to deduct technical issues for implementing such a service provision unit as the UE-centered zone, which is differentiated from such a service provision unit as a physical cell, and solve the technical issues.
And, appearance of the small cell may have a strong influence on a current RAN (remote area network). In particular, in the aspect of energy saving, on/off characteristic of the small cell may have an influence on deployment of a macro cell.